The present invention relates to a new and improved construction of an apparatus for mutually or selectively positioning towards one another roll surfaces of rolls, especially the intermediate rolls in a roll calender. More specifically, the positioning apparatus of the present development is suitable for lifting the roll surfaces, relieving the roll surfaces, lowering the roll surfaces from one work position into another desired position and retaining them in such other desired position.
In particular, such a positioning device serves for rapidly retracting or moving away from one another the roll surfaces throughout a defined path and for relieving the same for the purpose of compensating for undesired weights, among others also the so-called edge or marginal loads at the individual rolls.
Although surely such type of apparatus has also found utility in other technological fields for the positioning of at least two work surfaces relative to one another and which serve to apply pressure to a material layer or web for its treatment, roll calenders for the treatment or finishing of material webs constitutes a typical field of application of the present invention.
It is well-known in this technology that the line force at the contact locations or nip between the roll surfaces, through which there is guided the treated material webs or the like, must be exactly adjustable throughout the web width. This is necessary to ensure that the material web experiences at all locations throughout its entire width a desired web treatment, so that there can be obtained a desired quality of the treated product.
Also very small or minute undesired differences in the individual sections of the treated web can produce unusable products.
To augment the measures which are needed for this purpose there have been developed the so-called controlled deflection rolls or rolls with bending sag compensation, such as typically, for instance, the controlled deflection rolls commercially available under the trademark "NIPCO"-rolls, from the German firm Sulzer-Escher Wyss GmbH, located at Ravensburg, West Germany and which is also the assignee of the present development described herein. By means of these controlled deflection rolls it is possible to variably adjust or set at the contact locations of the mutually coacting rolls the desired line forces, also in zones or discrete regions throughout the web width.
The controlled deflection rolls have also been successfully utilized in multi-roll calenders for the treatment of paper webs, for instance typically as the lowermost and/or the uppermost roll and possibly also as an intermediate roll of the roll stack or set of the calender.
These controlled deflection rolls possess a stationary carrier or beam or yoke about which there is rotatably arranged a roll shell or jacket. Between the stationary carrier or beam and the rotatable roll shell or jacket there are disposed adjustable pressure or support elements, so that the rotatable roll shell or jacket is capable of also altering its position with respect to the stationary carrier or beam and, for instance, is freely movable in the pressing direction of the roll calender or rolling mill.
Apart from what has been previously explained, it is generally known to counteract the effect of the so-called overhanging weights or edge weights by roll relieving, in order to obtain the desired line forces in the individual roll nips. In this regard there is to be understood all of the weights which act externally of the edge of the material web upon the rolls and play a role during the loading of the rolls. These are, by way of example, the weight of the roll bearings and roll supports and different other weights, for instance the scrapers or doctor blades, deflection rolls and similar facilities which must be arranged at such external locations and which influence the loading action, that is to say, the bending-through or sag of the individual rolls.
To avoid the damaging action of the overhanging or cantilever weights there are known, by way of example, the provision of support structures which support the individual rolls at their journals, in other words as far as their force is concerned are directed against the direction of action of these loads or weights.
A further problem in the construction of roll calenders is the so-called rapid relief or relieving of the rolls or roll nips. In this connection there is to be understood a rapid retraction of the rolls in the set or stack from one another. This can be extremely important in the case where a disturbance arises, for instance when a material web which is to be treated ruptures. There are also known for such purpose solutions, for instance as disclosed in U.S. Pat. No. 4,266,475, granted May 12, 1981, wherein, for instance, during the rapid lowering of the lowermost roll of the roll set or stack the individual rolls remain suspended at a sequence of hydraulic arresting devices, so that in this manner they can be spaced from one another. The drawback of this arrangement or construction is that the entire weight of the roll set or stack, in other words all of the rolls are suspended at the holding device of the uppermost roll. However, according to the teachings of this aforementioned U.S. Pat. No. 4,266,475, there are not counteracted the marginal or edge loads.
For the rapid relief of the intermediate rolls and the relevant roll nip, there have been employed complicated and delicate spindles, gears or worm constructions, in order to thus operatively associate with each lowered or sinking roll a respective stop in each roll bearing region, so that at the completion of the roll relieving or nip opening operation the rolls assume or retain a defined spacing from one another.
These adjusting devices which operate as automatically as possible are required in multi-roll calenders for the reasons that there are employed rolls having surfaces formed of different materials, for instance rolls whose surfaces are formed of paper or cotton, wherein the diameter of the roll surface alters depending upon the subsequent roll machining operation or treatment work. Of course, there then also is altered the sum of the diameters of the effective or active regions of the roll bodies in a set or stack of such rolls and thus also the spatial position of the individual rolls.
Such holding devices also often times serve at the same time as facilities for raising a roll, particularly then when a roll of a larger diameter must be interchangeably mounted at the location of a roll of a smaller diameter.